Investigators say they need more flexibility to get warrants to allow hacking in such cases, especially when multiple computers are involved or the government doesn’t know where the suspect’s computer is physically located.

The Justice Department effort is raising questions among some technology advocates, who say the government should focus on fixing the holes in computer software that allow such hacking instead of exploiting them. Privacy advocates also warn government spyware could end up on innocent people’s computers if remote attacks are authorized against equipment whose ownership isn’t clear.

The Justice Department declined to provide further comment beyond the original documents.

The government’s push for rule changes sheds light on law enforcement’s use of remote hacking techniques, which are being deployed more frequently but have been protected behind a veil of secrecy for years.

In documents submitted by the government to the judicial system’s rule-making body this year, the government discussed using software to find suspected child pornographers who visited a U.S. site and concealed their identity using a strong anonymization tool called Tor.

The government’s hacking tools—such as sending an email embedded with code that installs spying software — resemble those used by criminal hackers. The government doesn’t describe these methods as hacking, preferring instead to use terms like “remote access” and “network investigative techniques.”

Right now, investigators who want to search property, including computers, generally need to get a warrant from a judge in the district where the property is located, according to federal court rules.

In a computer investigation, that might not be possible, because criminals can hide behind anonymizing technologies. In cases involving botnets—groups of hijacked computers—investigators might also want to search many machines at once without getting that many warrants.

Some judges have already granted warrants in cases when authorities don’t know where the machine is. But at least one judge has denied an application in part because of the current rules. The department also wants warrants to be allowed for multiple computers at the same time, as well as for searches of many related storage, email and social media accounts at once, as long as those accounts are accessed by the computer being searched.

“Remote searches of computers are often essential to the successful investigation” of computer crimes, Acting Assistant Attorney General Mythili Raman wrote in a letter to the judicial system’s rulemaking authority requesting the change in September. The government tries to obtain these “remote access warrants” mainly to “combat Internet anonymizing techniques,” the department said in a memo to the authority in March.

Some groups have raised questions about law enforcement’s use of hacking technologies, arguing that such tools mean the government is failing to help fix software problems exploited by criminals.

“It is crucial that we have a robust public debate about how the Fourth Amendment and federal law should limit the government’s use of malware and spyware within the U.S.,” said Nathan Wessler, a staff attorney at the American Civil Liberties Union who focuses on technology issues.

A Texas judge who denied a warrant application last year cited privacy concerns associated with sending malware when the location of the computer wasn’t known. He pointed out that a suspect opening an email infected with spyware could be doing so on a public computer, creating risk of information being collected from innocent people.

A former computer crimes prosecutor serving on an advisory committee of the U.S. Judicial Conference, which is reviewing the request, said he was concerned that allowing the search of multiple computers under a single warrant would violate the Fourth Amendment’s protections against overly broad searches.

The proposed rule is set to be debated by the Judicial Conference’s Advisory Committee on Criminal Rules in early April, after which it would be opened to public comment.

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The Law Blog covers the legal arena’s hot cases, emerging trends and big personalities. It’s brought to you by lead writer Jacob Gershman with contributions from across The Wall Street Journal’s staff. Jacob comes here after more than half a decade covering the bare-knuckle politics of New York State. His inside-the-room reporting left him steeped in legal and regulatory issues that continue to grab headlines.

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